A model for narcolepsy.

A model for narcolepsy is developed on the basis of data obtained from brains collected at post mortem from three patients with narcolepsy. The concentration of dopamine, noradrenaline, and serotonin and their metabolites was measured in many brain regions. The number and affinity of the 3-H-spiperone and 3-H-prazocin binding sites was also measured in many of these regions to characterize the D-2 dopamine and alpha-1-noradrenergic receptors, respectively. Evidence for significantly increased serotonin levels and serotonin turnover was found in many brain regions. Noradrenaline turnover was increased in the frontal cortex. DOPAC/DA was significantly reduced in the striatum. The number of D-2 dopamine receptors, however, was markedly increased in this region. The number of alpha-1-noradrenergic receptors was significantly decreased in the frontal cortex and amygdala. Our neurochemical data demonstrating increased NA and 5-HT turnover suggest that locus coeruleus noradrenergic neurones and raphe serotonergic neurones are overactive in narcolepsy. Current evidence posits that increased activity in these neurones depresses the activity of cholinergic pedunculopontine (PP) REM sleep effector neurones. PP neurones project to and stimulate the dopaminergic substantia nigra compacta neurones. Decreased PP activity in narcolepsy, thus, could lead to pontine cholinergic supersensitivity and could also reduce the firing rates of dopaminergic neurones, as the low striatal ratio of DOPAC/DA suggests. An increase in the number of D-2 dopamine receptors in the striatum may result. The reason for the increased activity of the noradrenergic and serotonergic neurones remains to be determined, but immune inactivation of alpha-1-noradrenergic receptors may be the initiating event. Low alpha-1-noradrenergic receptor numbers may account for the chronic drowsiness of narcolepsy. The repeated entry into sleep, and into REM sleep in particular, may represent a homeostatic response to increase these receptor numbers and, thus, to increase alertness. Some therapeutic implications of this model are presented in the discussion.     

Verbal reaction time patterns in aphasic adults: consideration for apraxia of speech

Verbal reaction time patterns were compared in aphasic adults presenting anterior and posterior left hemisphere lesions. Reaction Times were measured from simultaneous recording of the subjects' verbal responses and electromyographic activity from three oral-facial sites. Total Reaction Time was fractionated into Premotor Time and Motor Time components to assess latencies associated with motor speech planning and execution. The results suggested that only anterior lesions result in deficits in motor speech planning and/or execution while posterior lesion patients perform no differently than normal. The evidence supports traditional concepts regarding apraxia of speech as being associated with frontal lobe lesions.     

The Influence of Outcome Expectancy and Self-Efficacy on the Behavioral Intentions of Novice Exercisers

The present study was based upon self-efficacy (SE) theory (Bandura, 1986). Its purpose was to examine whether incentives, defined as the product of outcome expectancy and outcome value, would help to predict the behavioral intentions of novice exercisers when coupled with SE expectations for a specific form of exercise. Fifty- three volunteers who were novices at weight training for exercise, participated in a 2-day learn-to-weight-train clinic offered at a university. They completed pre- and postclinic measures of SE for weight training, expectancy-value ratings of outcomes primary and secondary to 1 month's weight-training participation, and a strength- of-intention measure of multiple actions consequent to clinic participation. Results indicated that primary physical health outcomes expected of postclinic participation independently predicted the variability in pre- and postclinic future intentions beyond the variance predicted by SE. Further, incentives and SE clearly discriminated between individuals extreme in the strength of their intentions at pre- and postclinic. Discussion concerns the inclusion of measures of incentive in studies using self-efficacy theory in order to examine individuals who begin exercise and then move through various decision stages about exercise adoption and maintenance. Rather than merely assuming the influence of incentives necessary and sufficient to encourage a cognitive or behavioral impact of efficacy, arguments are made for actively examining incentive as manifested through outcome expectations.     

AN EXPERIMENTAL COMPARISON OF THREE DIFFERENT SCHEDULES OF REINFORCEMENT OF DRUG ABSTINENCE USING CIGARETTE SMOKING AS AN EXEMPLAR

The efficacy of three different schedules of reinforcement for promoting and sustaining drug abstinence was compared in this study. Cigarette smoking was studied as an exemplar of stimulant drug self-administration. Sixty cigarette smokers were assigned to one of three groups (progressive rate of reinforcement, fixed rate of reinforcement, and yoked control). Participants in all three groups were asked to refrain from smoking for 1 week. Participants in the progressive and fixed groups achieved greater mean levels of abstinence than those in the control group. Participants in the progressive group were significantly less likely to resume smoking when they became abstinent than participants in the other groups.